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Biomedical subjects

S Ray

Publications and source records attributed to S Ray.

At least 109 records · Page 6Linked to original sources
PubMed1999

Altered lipid peroxidation and antioxidant potential in human uterine tumors.

A comparative study of lipid peroxidation and antioxidant potential has been made in human uterus and uterine tumor. Two types of uterine tumor used are: tumor (I), a fibroid which is the commonest benign solid tumor in uterus and tumor (II), an adenomyoma. Tumor microsomes are less susceptible to lipid peroxidation induced by both enzymic (NADPH-ADP-Fe3+ and xanthine-xanthine-oxidase) and non-enzymic (ascorbate-Fe2+) systems except in the case of tumor (II) microsomes when induced with xanthine-xanthine oxidase. Resistance of tumor microsomes to lipid peroxidation is associated with the low content of substrates in the form of polyunsaturated fatty acids (PUFAs), higher level of alpha-tocopherol, reduced glutathione and protein thiols and altered enzymic antioxidant potential (catalase and superoxide dismutase).

Antioxidants↗
PubMed1999

Effect of ammonium and nitrate ratio on glucose oxidase activity during gluconic acid fermentation by a mutant strain of Aspergillus niger.

Of the factors tested, the source and concentration of carbon and nitrogen in the medium exerted maximum effect on growth and acid production. Glucose (15%) and urea (0.14%) induced glucose oxidase synthesis and optimum yield of calcium gluconate. Potassium dihydrogen phosphate (0.2%) and magnesium sulphate (0.06%) stimulated glucose oxidase activity and calcium gluconate production. Borax at a concentration of 1.5 g/L induced maximum glucose oxidase and calcium gluconate production with increased glucose utilization.

Aspergillus niger↗
PubMed1999

Regulatory molecules in tumor metastasis.

The most life-threatening aspects of cancer are invasion and metastasis. The phenomena of metastasis is a multistep process of host tumor interactions. In the present study, we wanted to identify regulatory molecules in tumor metastasis. Our comparative studies between highly metastatic B16F10 and low metastatic B16F1 tumor cells strongly indicate that the function of vitronectin integrin receptor (alphavbeta3) and collagenase enzyme activity (72 kDa) are two of the key factors that control the invasive and metastatic properties of B16 F10 melanoma cells. The decreased expression of nm23 gene product, TIMP-2, and E-cadherin and the increased expression of pp125FAK in highly metastatic B16F10 tumor cells indicate their potential role in metastatic cascade.

Animals↗
PubMed1999

Behavioral development and olfactory learning in the honeybee (Apis mellifera).

Honeybees (Apis mellifera) can be readily conditioned in the laboratory to specific odors paired with a subsequent sucrose reward. A series of experiments are reported which demonstrate that the ability of bees to acquire and retain this learning is affected by the stage of behavioral development (caste). Results show rapid acquisition of the proboscis extension reflex (PER) conditioning in adult forager bees, however much slower acquisition and poorer retention of the same learning paradigm in younger adults, i.e., nurse bees and guard bees. Further, if nurse bees are made to forage precocially by manipulation of the hive population, these bees show excellent acquisition and retention of PER conditioning comparable to normal adult forager bees. Results are discussed in terms of olfactory learning requirements of bees performing caste-specific behaviors and the maturation of the bee nervous system.

Age Factors↗
PubMed1998

Role of calpain in spinal cord injury: effects of calpain and free radical inhibitors.

The demonstration of increased calpain activity, immunostaining, and expression at the gene (mRNA) and protein levels concomitant with ultrastructural degeneration and loss of axon and myelin proteins in lesioned cord have implicated a pivotal role for calpain in tissue destruction in spinal cord injury (SCI). Calpain, stimulated by free radicals, also mediates apoptotic cell death. These findings suggested that the use of calpain and lipid peroxidation drugs as therapeutic agents would protect cells and maintain the axon-myelin structural unit by preventing protein degradation. In order to examine this hypothesis, we treated SCI animals with calpain inhibitors (calpeptin) and/or methlprednisolone (MP), and antiinflammatory and free-radical inhibitor. SCI (40 g/cm) was induced by weight-drop, and 1 mg calpeptin or 165 mg MP/kg were given intravenously (i.v.) for 24 hours. Untreated injured animals receiving vehicle served as controls. Lesion 68-kDa and 200-kDa neurofilament proteins (NFPs) were analyzed by sodium dodecylsulfate polyarcylamide gel electrophoresis (SDS-PAGE) and chemiluminescence, and the extent of protein loss was quantitated. Loss of protein in the lesion of untreated cord amounted to 47% compared to sham control, while that for calpeptin- or MP-treated rats was 25-30%. Combination treatment with calpeptin and MP was slightly more effective in preventing NFP degradation, compared to either when used alone. Apopotic cell death in SCI as characterized by internucleosomal DNA fragmentation was also reduced following treatment with the inhibitors. The inhibition of cytoskeletal protein degradation suggests that calpain and free-radical inhibitors may rescue cells and preserve and maintain membrane structure by preventing protein breakdown, preserving motor function, and being neuroprotective.

Animals↗
PubMed1998

Prolonged STAT1 activation related to the growth arrest of malignant lymphoma cells by interferon-alpha.

Multiple biologic effects of interferon-alpha (IFN-alpha), including cell growth inhibition and antiviral protection, are initiated by tyrosine phosphorylation of STAT proteins. Although this signal pathway has been intensively investigated, the relevance of STAT signal persistence has received scant attention. Using paired isogenic lymphoma cells (Daudi), which either are sensitive or resistant to growth inhibition by IFN-alpha, we found comparable initial tyrosine phosphorylation of multiple STAT proteins; however, the phosphorylation durations and associated DNA-binding activities diverged. Phosphorylation and DNA-binding capacity of STAT1 decreased after 4 to 8 hours in resistant cells, as compared with 24 to 32 hours in sensitive cells, whereas phosphorylation of STAT3 and STAT5b was briefer in both lines. Functional significance of the prolonged STAT1 signal, therefore, was explored by experimental interruption of tyrosine phosphorylation, either by premature withdrawal of the IFN-alpha or deferred addition of pharmacologically diverse antagonists: staurosporine (protein kinase inhibitor), phorbol 12-myristate 13-acetate (growth promoter), or aurintricarboxylic acid (ligand competitor). Results indicated that an approximately 18-hour period of continued STAT1 phosphorylation was associated with growth arrest, but that antiviral protection developed earlier. These differences provide novel evidence of a temporal dimension to IFN-alpha signal specificity and show that duration of STAT1 activation may be a critical variable in malignant cell responsiveness to antiproliferative therapy.

Antineoplastic Agents↗
PubMed1998

Is absence of pyruvate dehydrogenase complex in mitochondria a possible explanation of significant aerobic glycolysis by normal human leukocytes?

The oxygen consumption of leukocyte mitochondria of both healthy donors and leukemic patients was tested by using different respiratory substrates. The results indicate that pyruvate could not be utilized by mitochondria of normal leukocytes, whereas mitochondria of leukemic leukocytes could use pyruvate as a good respiratory substrate. A search for the possible presence of pyruvate dehydrogenase complex (PDC) in leukocytes indicates that this enzyme is apparently absent in mitochondria of normal leukocytes but is quite active in mitochondria of leukemic leukocytes. The absence of PDC in normal leukocyte mitochondria can explain the phenomenon of significant aerobic glycolysis that has been observed in normal leukocytes.

Acetyl Coenzyme A↗
PubMed1998

Simulation of CPMAS signals at high spinning speeds.

The spin dynamics of an S(1/2)IN system during the CP mixing time of continuous wave and variable amplitude cross-polarization magic angle spinning (CWCPMAS and VACPMAS) experiments is discussed. The signal enhancement of a low abundant S spin, coupled to a set of N = 6 coupled spins with I = 1/2, is evaluated as a function of the length of the mixing time. For CWCPMAS this signal is first evaluated in the frequency domain and then transformed to the time domain. These calculations provide some additional insight into the CP spin dynamics and enable a practical approach toward the evaluation of CP signals of large spin systems. In addition the adiabatic character of the ramped VACPMAS experiments is discussed and S-spin signals of a spin system with N = 6 are simulated. Estimates of the upper bounds of the CP signals as a function of the number of I spins in an S(1/2)IN system are given and compared with the calculated values.

Magnetic Resonance Spectroscopy↗
PubMed1998

Proton MAS NMR spectra at high magnetic fields and high spinning frequencies: spectral simulations using floquet theory.

Proton magic angle spinning (MAS) spectra of a model spin system, consisting of six protons, were calculated for different values of the external magnetic field and the spinning frequencies. Floquet theory was used to evaluate these spectra. The reduction of the effective homonuclear dipolar interaction for increasing spinning frequency was investigated. The influence of an increase of the external magnetic field and the spinning frequencies on the linewidths of the centerband spectra is discussed. This Floquet description of the rotating proton spin system will assist us in our calculations of the CPMAS spin dynamics of a low abundant spin interacting with a set of coupled protons.

Magnetic Resonance Spectroscopy↗
PubMed1998

Comparative levels of organochlorine compounds in flounders from the northeast coast of Newfoundland and an offshore site.

Muscle tissue of yellowtail flounder, Pleuronectes ferruginea (n = 6) and winter flounder, Pseudopleuronectes americanus (n = 9) collected from Bonavista Bay, Conception Bay and an offshore location off northeastern Newfoundland, Canada, were analyzed for PCBs and other organochlorine compounds to determine if there are geographical variations in the concentrations and patterns of these persistent contaminants. The concentrations of total PCB congeners on a wet weight basis were relatively homogeneous at low ng/g levels. DDE, HCH compounds, and components of technical chlordane were the dominant organochlorine contaminants. Lipid normalized data indicate that PCB concentrations were higher in both species collected in the moderately urbanized region of Conception Bay. Principal Component Analysis (PCA) of PCB congener patterns indicated that flounder collected in Conception Bay had greater proportions of highly chlorinated PCB congeners, which may indicate point-source contamination in this region. Concentrations and patterns of other organochlorine compounds were relatively consistent across all sampling locations.

Animals↗
PubMed1998

Sexual behaviour and risk assessment of HIV seroconvertors among urban male factory workers in Zimbabwe.

Despite extensive HIV prevention programmes and knowledge of people dying of AIDS, people in Zimbabwe continue to be infected with HIV and other sexually transmitted infections (STIs). This paper presents selected case histories from interviews with 57 men who became HIV positive during follow up of 1678 seronegative male factory workers in Harare, and describes the circumstances in which they were exposed to infection. Youth was a major risk factor, with 47% of those who seroconverted aged between 18 and 24 yr. STIs were reported by 23% of the group in the seroconversion period, a marker of unprotected sex. Individuals did not recognise themselves or their partners as candidates for infection because of categorisation of high risk groups as "promiscuous" or clients of sex workers. Many were optimistic that they had changed sufficiently by using condoms more often or by avoiding sex workers. They made inaccurate assessments of who was safe for unprotected sex, based on judgements about their character, background and age. Over 40% of the seroconvertors had previously been counselled on staying HIV negative. Community approaches which nurture development of supportive group norms, respect for human rights and responsibilities, and safe environments for disclosure of HIV status, are vital for overcoming denial of risk at individual and societal levels. Special efforts targeted at youth are crucial since they have the highest risk of new infections and include use of media, drama, role models, advisory centres, peer education programmes. Health professionals need training and skills to enable people at risk of HIV infection to devise strategies based on more realistic personal risk assessment.

Adolescent↗
PubMed1998

The integration of object properties.

Is a complex object learned as a whole from the onset of learning, or is property recall fragmented and only integrated with repeated experience? The authors studied the recall of 3-property visual objects and found that even when property recall was low, recall coherence was high. Properties not organized as visual objects did not show high recall coherence. In addition, the authors failed to find evidence that spatial location, spatial proximity, spatial distinctiveness, distinctive motion, or perceptual grouping induced by common motion affected the integration of properties. Unitariness, temporal contiguity, and intention, however, were factors that influenced memory coherence. The authors concluded that integration occurs when properties are encoded as the constituents of a cognitive structure.

Humans↗
PubMed1998

Frequency and prognostic implications of conduction defects in acute myocardial infarction since the introduction of thrombolytic therapy.

OBJECTIVE: To document the frequency of conduction defects and their influence on prognosis in a large series of patients with acute myocardial infarction who underwent coronary care during a period when thrombolytic therapy was in common usage. BACKGROUND: Conduction defects have been associated with an adverse prognosis following acute myocardial infarction, but there are few data on the incidence and outcome of conduction defects since the introduction of thrombolytic therapy. PATIENTS AND METHODS: The study group comprised 1225 consecutive patients with acute myocardial infarction treated in the coronary care unit from 1 January 1988 to 31 December 1994. Conduction defects were recorded prospectively and were classified as follows: complete atrioventricular node block associated with narrow complex escape rhythms; left or right bundle branch block; bifascicular block; complete heart block involving both bundle branches. RESULTS: Electrocardiographic data were available in 1220 patients. Complete atrioventricular node block occurred in 65 (5.3%), left and right bundle branch block in 29 (2.4%) and 44 (3.6%) bifascicular block in 36 (2.9%) and complete heart block involving both bundle branches in 20 (1.6%). The more advanced degrees of block in the bundle branches occurred more commonly in patients with diabetes, previous infarction. Q-wave infarction, anterior infarction and left ventricular failure. Survival analysis showed an increased short- and long-term cardiac mortality in patients with conduction defects, prognosis worsening as the severity of the conduction defect increased. CONCLUSION: Conduction defects complicated acute myocardial infarction in 16% of cases and had a graded impact on the short- and long-term prognosis, patients with advanced bundle branch involvement faring worst. The data showed a small decline in the rate of severe conduction defects compared with previous studies, possibly reflecting the beneficial effects of thrombolytic therapy on infarct size.

Adult↗
PubMed1998

Genetic mapping of a major locus controlling pyrethroid resistance in Tribolium castaneum (Coleoptera: Tenebrionidae).

Tribolium castaneum (Herbst) strain QTC279 is highly resistant to deltamethrin and other synthetic pyrethroids. This strain was shown to carry at least 1 resistance gene, PyR-1, on linkage group 9, approximately 20 map units from the visible mutant marker, pearl. Three-point mapping involving pearl and another visible mutant marker, cola, indicated a gene order of pearl-cola-PyR-1. Evidence of a 2nd LG9-linked resistance factor (R) mapping in the gene order R-p-co was also observed. Other resistance factors were clearly present in QTC279, but were not genetically mapped. Piperonyl butoxide, an inhibitor of cytochrome P450-mediated oxidative metabolism, significantly increased the toxicity of deltamethrin to a strain derived from QTC279 that carries PyR-1, strain pR. Compared to susceptible beetles, QTC279 and pR had elevated and comparable levels of cytochrome P450 protein. The significance of pyrethroid resistance in T. castaneum is discussed.

Animals↗
PubMed1998

Diospyrin, a bisnaphthoquinone: a novel inhibitor of type I DNA topoisomerase of Leishmania donovani.

Diospyrin is a plant product that has significant inhibitory effect on the growth of Leishmania donovani promastigotes. This compound inhibits the catalytic activity of DNA topoisomerase I of the parasite. Like camptothecin, it induces topoisomerase I mediated DNA cleavage in vitro. Treatment of DNA with diospyrin before addition of topoisomerase I has no effect. Preincubation of topoisomerase I with diospyrin before the addition of DNA in the relaxation reaction increases this inhibition. Our results suggest that this bis-naphthoquinone compound exerts its inhibitory effect by binding with the enzyme and stabilizing the topoisomerase I-DNA "cleavable complex." Diospyrin is a specific inhibitor of the parasitic topoisomerase I. It does not inhibit type II topoisomerase of L. donovani and requires much higher concentrations to inhibit type I topoisomerase of calf thymus. The potent inhibitory effect of diospyrin on type I DNA topoisomerase from L. donovani can be exploited for rational drug design in human leishmaniasis.

Animals↗
PubMed1998

Minimally invasive aortic valve replacement through a transverse sternotomy: a word of caution.

OBJECTIVES: To compare aortic valve replacement (AVR) using a minimally invasive approach through a transverse sternotomy with the established approach of median sternotomy. DESIGN: Retrospective, case-control study. PATIENTS: Fourteen high risk patients (median age 78, Parsonnet score of 18%) who underwent AVR performed through a minimally invasive transverse sternotomy were compared with a historical group of patients matched for age, sex, and Parsonnet score who underwent AVR performed through a median sternotomy by the same surgeon. OUTCOME MEASURES: Cross clamp time, total bypass time, intensive care stay, postoperative in-hospital stay, morbidity, and mortality. RESULTS: There were two deaths in the minimally invasive group and none in the control group (NS). The cross clamp and total bypass times were longer in the minimally invasive group (67 and 92 minutes v 46 and 66 minutes, p < 0.001). There was a higher incidence of re-exploration for bleeding (14% v 0%) and paravalvar leaks (21% v 0%) in the minimally invasive group but these differences were not significant. The minimally invasive group had a longer postoperative in-hospital stay (p = 0.025). The incidence of mortality or major morbidity was 43% (six of 14) in the minimally invasive group and 7% (one of 14) in the matched pairs (p = 0.013). CONCLUSIONS: AVR can be performed through a transverse sternotomy but the operation takes longer and there is an unacceptably high incidence of morbidity and mortality.

Aged↗